1. Field of the Invention
The invention relates to an antenna, and more particularly to an antenna with increased bandwidth.
2. Description of the Related Art
U.S. Pat. No. 6,812,892, U.S. Pat. No. 7,161,543 and U.S. Pat. No. 6.891.504 disclose three conventional antennas, wherein the conventional antennas have narrow bandwidths, and cannot satisfy present transmission requirements. For example, FIG. 1a shows a conventional antenna 1 disclosed in U.S. Pat. No. 6,812,892, which has a ground element 10, a conductive element 20 and a radiator 30. The conductive element 20 is connected to the ground element 10. The radiator 30 is connected to the conductive element 20. A coaxial cable 40 is electrically connected to the ground element 10 and the conductive element 20. The radiator 30 has a first section 31 and a second section 32. The first section 31 transmits a high frequency signal, and the second section 32 transmits a low frequency signal.
FIG. 1b shows signal transmission of the conventional antenna 1, wherein the bandwidth of the antenna 1 (bandwidth is defined as signals having voltage standing wave ratio less than 2) is between about 2.39 GHz to 2.53 GHz and between 4.84 GHz to 5.80 GHz. The conventional antennas have narrow bandwidth, and cannot satisfy present transmission requirements.